Low-pressure hydrothermal processing of mixed polyolefin wastes into clean fuels

摘要

The amount of polyolefin waste, which is 63% of the total plastic waste, has grown exponentially over the past six decades. Its degradation products pose a serious threat to ecosystems and human health. Polyolefins can be converted to clean oils or fuels by using the supercritical water liquefaction (SWL) method at high pressures (23 MPa), which require high capital and energy costs. A new low-pressure (-2 MPa) hydrothermal processing (LP-HTP) method is developed to convert polyolefin waste with 50% or more polypropylene into oils with 87% yield at 450 ?C and 45 min. The oils, which are C4 to C25 hydrocarbons, can be distilled into clean gasoline and ultra-low sulfur diesel. With this method, up to 190 million tons of fuels can be produced annually from polyolefin waste, resulting in savings of 92% of the energy and 71% of the GHG emissions compared to conventional methods for producing fuels.